We run two field experiments on team diversity in a large undergraduate economics class. Small groups with random compositions are generated and assigned team tasks. In the first experiment, tasks are creative and complex, while in the second one they are more standard. We use a multidimensional measure of diversity based on gender, race, and migration status. We estimate its impact on teamwork quality and group performance. We find a significant U-shaped effect on teamwork quality in both experiments. However, the impact on performance depends on the type of task: it is positive for creative tasks, but negative for standard ones. We interpret
these results as the consequence of two conflicting forces: diversity is a source of creativity, but it can hamper communication and coordination between team members. When tasks are creative, the first (positive) force dominates; for standard tasks, instead, communication challenges do. The U-shaped impact on teamwork quality suggests that faultlines – dividing lines that split a
group into subgroups based on demographic characteristics – can cause inter-subgroup cohesion
to break down, while very homogeneous or very heterogeneous groups collaborate better. These results allow us to build a comprehensive framework to better understand the impact of diversity on teamwork
